Consumers of industrial gases demand higher and higher purities of such gases wherein impurity contents must be determined, quantified, qualified and monitored down to exceedingly low levels of such impurities typically in the parts per million, parts per billion and in some instances, parts per trillion. Industrial gases being utilized by sensitive manufacturing operations such as semi conductor fabrication facilities, require exceedingly low levels of impurities in gases used in semiconductor fabrication processes, such gases such as hydrogen and oxygen. Various analytical techniques are presently utilized to determine impurity levels in industrial gases such as those supplied to semiconductor fabrication facilities. One such detection device utilized for sensitivity to impurities, particularly at low levels, is an atmospheric pressure ionization mass spectrometer ("APIMS"). Mass spectrometers are known analytical detection devices such as is described in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, (1978), Vol. 2, page 600 to 650.
The prior art has broadly described various techniques for separating mixtures of gases, such as hydrogen or oxygen from helium. One such agent useful for selective absorption of oxygen from other gases is the family of inorganic compositions called perovskite. Perovskites possess a cubic crystal structure comprised of ABO.sub.3, such as mineral perovskite, CaTiO.sub.3. These perovskites are identified in U.S. Pat. No. 4,957,718. Analogous perovskite materials and applications are identified i n U.S. Pat. Nos. 4,748,143 and 5,071,626.
Other material s useful for selective oxygen adsorption from mixed gas streams include cyanocobaltate complexes as identified in U.S. Pat. No. 5,141,725.
It is also known to remove carrier gases such as hydrogen in the feed to a mass spectrometer by diffusion through palladium. See Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, (1978), Vol. 2, page 644.
Some industrial gases, such as nitrogen, helium and argon, can be analyzed for low level impurity detection directly by injection of a sample of such gas into an APIMS. Hydrogen has been evaluated for impurity content in direct injection into a mass spectrometer, but certain impurities are not readily distinguishable in hydrogen using the best mass spectrometer capabilities. Presently, oxygen cannot be evaluated for potential impurities by direct injection in an APIMS. Therefore, a need exists for a method for detecting and analyzing impurities of a broad spectrum in hydrogen and a comparable need to analyze oxygen for any impurity is also sought.
The present invention overcomes the difficulties in analyzing and detecting low concentration levels of impurities in industrial gases destined for high purity end uses by effectively transferring the impurities to a high ionization potential gas and selectively removing the gas being sampled before detection in an appropriate detector for concentration and quantification of such impurities, as will be set forth in greater detail below.